1. Field of the Invention
The present invention relates to a centrifuge rotor and, in particular, to a centrifuge rotor having a liquid containment arrangement adapted to contain any liquid spilled within the rotor and to prevent contamination of the centrifuge by that spilled liquid.
2. Description of the Prior Art
A centrifuge rotor is a device adapted to expose a sample carried in a suitable sample container to a predetermined centrifugal force field. This field is achieved by causing the rotor to rotate at a selected angular velocity, typically in the range from ten thousand to approximately eighty thousand revolutions per minute.
The rotor is provided with an annular array of sample receiving cavities which are disposed concentrically about the axis of rotation of the rotor. If the longitudinal axis of each of the cavities is inclined toward the rotational axis of the rotor, the device is known as a fixed angle rotor.
The samples are each contained in a container which, in the typical application, is closed by a suitable capping arrangement. The capping arrangement is necessary in the event that the sample is a biologically hazardous material to insure that the sample is appropriately isolated from the environment.
When the sample is not hazardous the capping arrangement may be omitted so long as the operator fills the tube only to a predetermined level. It should be noted that since the tubes are received in the inclined cavities in the rotor the predetermined level to which the tube is filled lies some distance below the rim of the tube. Care must be exercised to insure that the tube is filled only to this level to guard against the possibility that centrifugal force effects will cause the contents of the tube to overflow and spill from the inclined tube when the tube is inserted into the rotor and rotated to its operational speed.
The containers are themselves susceptible to rupture. Thus, even if a capping arrangement has been used, and even if the operator has exercised care to introduce only the proper volume of liquid into the container, there still may occur instances in which the liquid contents of the tube will spill into the rotor.
As a further precaution to prevent the egress of the spilled liquid from the rotor, a cover may be provided over the rotor. The cover has a depending skirt which seats against an upstanding rim of the rotor. When secured in place the skirt and the rim cooperate to confine the liquid within the rotor. Exemplary of such a structure is the device shown in U.S. Pat. No. 3,819,111 (Romanauskas et al.), assigned to the assignee of the present invention. U.S. Pat. No. 4,202,487 (Edwards) and U.S. Pat. No. 4,360,151 (Cowell et al.) describe other rotor covers for use in a centrifuge instrument.
A cover may itself become dislodged from the rotor due to the centrifugally induced force of the spilled liquid acting against the underside of the cover. Structural arrangements which eliminate this occurrence by isolating the cover from the spill are known in the art. U.S. Pat. No. 4,372,483 (Wright) discloses a centrifuge rotor having an annular liquid containment lip machined into the body of the rotor above the tube cavities. The lip serves to confine any liquid present due to container rupture, cap leakage or inadvertent excessive filling. The annular lip extends radially inwardly to overlie a portion of the cavities to confine any liquid liberated into the body of the rotor. The lip prevents the liquid from contacting and exerting pressure on the cover of the rotor.
Although each of the above discussed alternatives appears to adequately confine any spilled liquid to the interior of the rotor, none of these expedients confronts or solves the problem of contamination of the rotor by the spilled liquid as the rotor slows to a stop. For example, if a tube ruptures and the containment annulus shown in the last-mentioned patent functions in the intended manner then the spilled liquid is confined on the interior of the rotor. However, as the rotor slows the liquid drains down from the region of the confinement lip into the cavities and onto the other containers carried in the rotor. It is possible that the draining liquid may possibly enter into the other containers, thus compromising the contents of these containers. The draining liquid may also contaminate other parts of the rotor, making subsequent handling of the containers and the rotor itself more difficult or more hazardous for the operator.
In view of the foregoing it is believed advantageous to provide a centrifuge rotor which, in the event of liquid spillage, serves to prevent the contamination of other rotor cavities, other containers or the interior of the rotor.